An airplane is in level flight over Antarctica, where the magnetic field of the earth is mostly directed upward away from the ground. As viewed by a passenger facing toward the front of the plane, is the left or the right wingtip at higher potential? Does

your answer depend on the direction the plane is flying?

It is the force on moving charge in presence of magnetic field.

It is given by

$\mathrm{F}=\mathrm{q}\left(\mathrm{v}\times \mathrm{B}\right)$

Where, F is the Lorentz force, v is the velocity of the particle and B is the applied magnetic field and q is charge of the particle.

If the airplane’s wingtips are made up of a conductor that contains lots of free charges and moves in a forwarding direction. As the magnetic field of the earth is acting in an upward direction. So, according to Lorentz’s force, the magnetic force exerted on the positive charge must be in the right direction which causes charges to migrate in the right wingtip making it at higher potential.

When the airplane reverses the direction of flying, the magnetic force also reverses in direction, therefore, the negative charge is now shifted to the left wingtip which means the right wingtip is now at the left and still at higher potential.

Hence, the right wingtip is always at higher potential and it does not depend on the direction of the plane.